Quote:
Originally Posted by russellw
There is a rogue apache process running so the only option will be a server restart which I am about to do.
Current Time: Sunday, 25-May-2014 21:13:03 EST
CPU Usage: u31649.9 s141.1 cu74.97 cs0 - 468% CPU load
39.8 requests/sec - 0.6 MB/second - 15.8 kB/request
300 requests currently being processed, 0 idle workers
Cheers
Russ
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0 idle workers might explain it. You can try jacking the number of worker processes up but it's a slippery slope if the machine is heavily loaded. No sure how many CPUs the box has but you want to keep the utilisation manageable.
With this type of web application you can pretty much assume that it is database service times that are causing the slow web response times and that is what you have to optimise. Not sure what optimisations you have already put into vbulletin but if the avatars or attachments are stored in the DB move them onto the file system. After that you need to look at SQL optimisation and possibly memcache. Then look at upgrading to the latest version of mysql as they normally include performance optimisations in the newer releases.
After you have looked at all that then have a look at process priorities for mysql. You can jack the process priority of the database processes to give them priority over other processes. This helps performance when running mixed workload (web server and database server) and the run queues are long.
There are other things you can do like setting noatime on the volumes for the database and webserver files. This just stops the OS from updating the last access time on the files. It is redundant for a server like this and slows things down. You need to modify the /etc/fstab file with the noatime option and remount.
As a first step monitor the worker processes and if you often have 0 free then increase it a bit at a time and monitor performance. Also grab a snapshot of the machine using vmstat 5 5 when performance is slow.